Passive RFID antennas implemented as HDX and FDX ear tags are widely used for the tracking and identification of animals. The antennas are provided in plastic RFID tags, with the antenna (transponder) coil and required electronics being molded into a plastic button that is attached to the animal's ear. The ear tag consists of two parts, with one being the encapsulated transponder coil and electronics and the other containing a mounting needle embedded in plastic that pierces the animal's ear and attaches to the part containing the transponder coil and electronics so as to fix it on the ear and ensure that the ear tag cannot be removed without destroying it. When gathering information from the RFID tags attached to an animal's ear, it is often required to hold the read/write (R/W) unit a relatively large distance from the animal, which requires an antenna with increased performance in order to increase the voltage at the antenna terminals so that the antenna can transmit and receive RF signals over a (relatively large) distances. One way of improving the performance of an RFID antenna is to increase the quality factor Q of the antenna. This can be done by using litz wire to form the antenna coil, which leads to an improved performance of the RFID tag, but is rather expensive.
Another conventional solution to increase Q involves placing a ferrite material e.g. a ferrite stick within the coil. The ferrite may be provided as a stick inside the mounting needle. Using ferrite in the RFID tags as described above significantly improves the Q of the antenna coils contained therein. However, the ferrite is exposed to mechanical stress, while fixing the ear tag and tends to break due to its rigidity. Furthermore, the increase of Q is limited due to the ferrite's stick-like shape.